This invention relates to a method for improving the mechanical properties of soil and its resistance to erosion, a polymeric solution therefore, and to a process for preparing the polymeric solution.
Soil erosion is a phenomenon occurring in a wide variety of situations. For example, it is a serious problem in countries with arid climates and in areas with very little rain fall. Soil erosion problems are frequently caused by the existence of fine particles on the surface of the soil. These fine particles are poorly bonded together and susceptible to erosion by wind and rain.
In addition, the structure of the soil determines its properties such as permeability to water, porosity, crust formation, load carrying capacity, etc. And weak soil and sand structure cause problems in road and highway construction, steep slopes, water channels, construction, excavation banks, landing sites for aircraft and the like.
Extensive research has been carried out in an endeavor to improve soil structure, to reduce soil erosion, to reduce water evaporation and to increase the bonding strength so that it can withstand greater loads. In essence, the research has for the most part had one or two objectives, i.e. to prevent or minimize soil erosion and to improve a soil load carrying capacity.
For example, previous research has disclosed the use of acrylamide polymer cross-linked with N, N-methylene bisacrylamide with other additives such as palm nuts and seaweed as water absorbing material for agricultural applications. Others have used acrylamide polymer as plant growing media.
A number of researchers have used polymer based materials to stabilize the soil. For example, they have used cellulosic polymers with Al(OH).sub.3, latex, lignosulfonates reacted with acrylic acid, polyacrylamide reacted with polyaldehydes and hypohalites, mixtures of dimer diisocyanate and dimer diamine, polyelectrolytes, cationic polymer latexes prepared from acrylates and anionic lignin from cellulosic material, synthetic and rubber latexes with non-ionic surfactants.
In addition, the U.S. Pat. No. 3,495,412 discloses a process for forming a gel-like material in a soil by injecting into the soil an aqueous solution containing three components. The aqueous solution includes urea, formaldehyde and polyvinyl alcohol and is cured within the soil by the addition of an acidic substance. This process is useful for rendering a water-permeable soil water impermeable and thereby stabilizes it.
While most of the aforementioned techniques and compositions have been useful for improving soil structure and/or its resistance to erosion, they also have limitations. For example, toxic monomers such as acrylamide could leak into the water supply and present a health hazard to an operator who is applying it. Other systems are difficult to apply, some are in solid form and some cure slowly, and others are relatively expensive.